Bonding pad for preventing pad peeling

ABSTRACT

A bonding pad includes multiple metal layers, insulation layers disposed between the multiple metal layers, and a fixing pin coupled between the uppermost metal layer and an underlying metal layer of the multiple metal layers, where a bonding is performed on the uppermost metal layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority of Korean patent applicationnumber 10-2007-0070557, filed on Jul. 13, 2007, which is incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device, and moreparticularly, to a bonding pad for preventing a pad from peeling in aball bonding, and a method for fabricating the same.

In the fabrication of a semiconductor device, wire bonding in apackaging process is an electrical interconnection technique. In thewire bonding, a metal pad of a bonding pad part provided in a chip iselectrically interconnected to a lead frame for connection to anexternal device. For example, in the wire bonding, a ball bonding isperformed over a metal pad. The bonding pad part to be bonded includesmultiple metal layers and insulation layers filling gaps between themultiple metal layers.

FIG. 1 illustrates a cross-sectional view of a typical bonding padstructure, and FIG. 2 illustrates a cross-sectional view for explaininga technical limitation of a typical ball bonding.

Referring to FIG. 1, the typical bonding pad includes a first metallayer M1, a second metal layer M2, and a third metal layer M3. A firstinsulation layer IMD1 is formed between the first metal layer M1 and thesecond metal layer M3, and a second insulation layer IMD2 is formedbetween the second metal layer M2 and the third metal layer M3. A ballbonding is performed on the uppermost layer, that is, the third metallayer M3.

In a subsequent package fabrication process, as illustrated in FIG. 2, aball bonding 11 is performed on a center of the third metal layer M3 inthe bonding pad of FIG. 1.

However, pressure generated by the ball bonding 11 is transferred to thesecond insulation layer IMD2 and the second metal layer M2, and arepulsive force 12 is transferred to edges of the third metal M3. Therepulsive force 12 causes a pad peeling 13 at the edges of the thirdmetal layer M3, leading to a ball bonding failure. That is, a peelingphenomenon occurs so that an attachment force of the pad is weakened andthe pad is peeled off.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to providing a bondingpad, which is capable of preventing a pad failure of a bonding padduring a bonding process, and a method for fabricating the same.

In accordance with an aspect of the present invention, a bonding pad isprovided. The bonding pad includes multiple metal layers, insulationlayers filled between the multiple metal layers, and a fixing pincoupled between the uppermost metal layer, where a bonding is performed,and the underlying metal layers.

In accordance with another aspect of the present invention, a method forfabricating a bonding pad is provided. The method includes forming afirst insulation layer, forming a plurality of slits over the firstinsulation layers, forming a second insulation layer over the slits,partially etching the second insulation layer and the first insulationlayer to form a contact hole penetrating an interval between the slits,forming a fixing pin filling the contact hole, and forming a metal layercoupled to the fixing pin and at which a bonding is to be performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a typical bonding padstructure.

FIG. 2 illustrates a cross-sectional view for explaining a technicallimitation of a typical ball bonding.

FIG. 3 illustrates a plan view of a bonding pad in accordance with anembodiment of the present invention.

FIG. 4A illustrates a perspective cross-sectional view taken along lineA-A′ of FIG. 3.

FIG. 4B illustrates a perspective view of a fixing pin in FIG. 4A.

FIGS. 5A to 5H illustrate cross-sectional views of a method forfabricating a bonding pad in accordance with a first embodiment of thepresent invention.

FIG. 6A illustrates a plan view of a bonding pad in accordance with asecond embodiment of the present invention.

FIG. 6B illustrates a perspective view of a fixing pin in accordancewith the second embodiment of the present invention.

FIG. 6C illustrates a plan view of a bonding pad in accordance with athird embodiment of the present invention.

FIG. 7A illustrates a plan view of a bonding pad in accordance with afourth embodiment of the present invention.

FIG. 7B illustrates a plan view of a bonding pad in accordance with afifth embodiment of the present invention.

FIG. 8A illustrates a plan view of a bonding pad in accordance with asixth embodiment of the present invention.

FIG. 8B illustrates a perspective cross-sectional view taken along lineA-A′ of FIG. 8A.

FIGS. 8C and 8D illustrate perspective views of a fixing pin and asecond metal layer in accordance with the sixth embodiment of thepresent invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, a bonding pad and a method for fabricating the same inaccordance with the present invention will be described in detail withreference to the accompanying drawings.

The present invention relates to a technique that can prevent a pad of abonding pad from peeling. The peeling is caused by pressure generatedduring a ball bonding. The technique may be applied to a pad formingprocess of a memory device where a ball bonding is performed on abonding pad part for a package. In addition, the present inventionrelates to a technique that can prevent any pad from peeling, which maybe caused in a process of forming a large pattern having the same shapeas a bonding pad.

A technical principle applied to the following embodiments is to form afixing pin for fixing a bonding pad to an outer empty area of a ballbonding region in a bonding pad forming process in order to prevent thepad from peeling. In addition, an upper portion of the fixing pin isformed in a shape of a wine glass to increase an attachment force withrespect to the uppermost metal layer, and a lower portion of the fixingpin is formed in a shape of a ball to fix it to a metal layer formedunder the uppermost metal layer, thereby preventing the fixing pin frombeing removed. In this way, the pad may be further prevented frompeeling.

FIG. 3 illustrates a plan view of a bonding pad in accordance with anembodiment of the present invention. FIG. 4A illustrates a perspectivecross-sectional view taken along line A-A′ of FIG. 3, and FIG. 4Billustrates a perspective view of a fixing pin in FIG. 4A.

Referring to FIG. 3, a bonding pad 100 includes multiple metal layers101 and insulation layers (not shown) filled between the multiple layers101. A fixing pin 103 is coupled between the uppermost metal layer andthe underlying metal layers at an outer area beyond the bonding region102.

It is assumed that the multiple metal layers 101 include a first metallayer, a second metal layer, and a third metal layer. The connectionstructure of the respective metal layers is well-known and is omittedfor convenience of description.

Referring to FIGS. 4A and 4B, the bonding pad 100 includes a first metallayer 101A, a plurality of lateral slits 101B formed of a second metallayer, and a third metal layer 101C. Unlike the second metal layer 101B,the first metal layer 101A and the third metal layer 101C are formed ina plate shape.

A fixing pin 103 is coupled between the third metal layer 101C and theslits 101B. That is, an upper portion of the fixing pin 103 is insertedinto and fixed to a lower portion of the third metal layer 101C, and alower portion of the fixing pin 103 is positioned between and is fixedunder two adjacent slits 101B.

As illustrated in FIG. 4B, the fixing pin 103 includes a disk portion103A, a pillar portion 103B, and a ball portion 103C. The disk portion103A of the fixing pin 103 is inserted into and fixed to a lower portionof the third metal layer 101C, and the pillar portion 103B of the fixingpin 103 is cylindrical and passes through a gap between the slits 101B.The ball portion 103C of the fixing pin 103 is formed under the gapbetween the adjacent slits 101B. Since the disk portion 103A has arounded lower portion and is coupled to the pillar portion 103B, thefixing pin 103 is formed in a shape of a wine glass. The ball portion103C of the fixing pin 103 has a diameter greater than a size of the gapbetween the slits 101B. It can be said that the disk portion 103A of thefixing pin 103 has a shape of a screw head.

In such a bonding pad 100, the fixing pin 103 can prevent the peeling ofthe uppermost metal layer, i.e., the third metal layer 101C, during thebonding process. In addition, the attachment force between the fixingpin 103 and the third metal layer 101C is further increased because thedisk portion 103A of the fixing pin 103 is rounded at the lower portion.Also, since the ball portion 103C of the fixing pin 103 has a diametergreater than the size of the gap between the slits 101B, the third metallayer 101C coupled to the fixing pin 103 is not removed. Since thefixing pin 103 is formed at the outer area of the bonding region, notbelow the bonding region, the pad peeling caused by the repulsive forceat the edges of the third metal layer 101C can be further prevented.

FIGS. 5A to 5H illustrate cross-sectional views of a method forfabricating a bonding pad in accordance with a first embodiment of thepresent invention.

Referring to FIG. 5A, a first metal layer 21 is formed and a firstinsulation layer 22 is formed over the first metal layer 21. The firstmetal layer 21 may include an aluminum layer or a copper layer, and thefirst insulation layer 22 may include an intermetal dielectric (IMD),for example, an oxide layer. The first insulation layer 22 is formed ofa low-k dielectric, which can reduce a parasitic capacitance between thefirst metal layer 21 and slits, which will be formed later.

A plurality of slits 23 formed of the second metal layer is formed overthe first insulation layer 22. The plurality of slits 23 are formed byforming the second metal layer and patterning the formed second metallayer so that the patterns are arranged in a slit shape. The pluralityof slits 23 has the same size and is arranged with the same spacing. Theslits 23 may include an aluminum layer or a copper layer.

A second insulation layer 24 is formed over the slits 23. The secondinsulation layer 24 is formed to fill the gaps between the slits 23. Thesecond insulation layer 24 may include an intermetal dielectric (IMD),for example, an oxide layer. The second insulation layer 24 is formed ofa low-k dielectric, which can reduce a parasitic capacitance between theslits 23 and a third metal layer, which will be formed later.

Referring to FIG. 5B, a contact mask 25 is formed over the secondinsulation layer 24 using a photoresist layer. The contact mask 25 hasan opening 25A formed with a predetermined size. The opening 25A definesa contact hole at an outer area of the bonding region.

A portion of the second insulation layer 24 is etched using the contactmask 25 to form a first contact hole 26A. A diameter of the firstcontact hole 26A is larger than a diameter of the opening 25A. To thisend, a portion of the second insulation layer 24 is etched using a wetetch process. The etched second insulation layer will be referred to asa primarily-etched second insulation layer 24A.

Referring to FIG. 5C, the primarily-etched second insulation layer 24Aunder the first contact hole 26A is further etched to form a secondcontact hole 26B having a vertical profile. In order to form the secondcontact hole 26B, a dry etch process is performed using the contact mask25 as an etch barrier.

The second contact hole 26B has a width smaller than the first contacthole 26A and a depth greater than the first contact hole 26A.Accordingly, the first contact hole 26A and the second contact hole 26Bare vertically connected to form a shape of a wine glass.

During the dry etch process for forming the second contact hole 26B, theprimarily-etched second insulation layer 24A formed between the slits 23and self-aligned by the slits 23 is further etched so that the secondcontact hole 26B is formed in the gap between the slits 23. A portion ofthe first insulation layer 22 under the slits 23 may be etched tofurther extend the depth of the second contact hole 26B. The secondinsulation layer 24 and the first insulation layer 22 etched during thedry etch process for forming the second contact hole 26B will bereferred to as a secondarily-etched second insulation layer 24B and aprimarily-etched first insulation layer 22A, respectively.

Referring to FIG. 5D, the primarily-etched first insulation layer 22Aformed under the second contact hole 26B is isotropically etched to froma third contact hole 26C. The third contact hole 26C formed by theisotropic etch process has a ball shape. A diameter of the third contacthole 26C is greater than the size of the gap between the slits 23.

The photoresist layer used as the contact mask 25 is removed by astripping process.

The contact hole 26 resulting from the removal of the contact mask 25includes the first contact hole 26A, the second contact hole 26B, andthe third contact hole 26C. Due to the first contact hole 26A, the upperportion of the contact hole 26 has a shape of a wine glass, and thediameter of the third contact hole 26C is greater than the size of thegap between the slits 23. Reference numeral 22B refers to asecondarily-etched first insulation layer etched during the process offorming the third contact hole 26C.

Referring to FIG. 5E, a fixing pin 27 is formed to fill the contact hole26. The fixing pin 27 is a plug that is formed by forming a tungstenlayer and performing an etch-back process on the formed tungsten layer.

Since the pattern of the contact hole (26 in FIG. 5D) is transferred,the fixing pin 27 has a structure in which a disk portion 27A, a pillarportion 27B, and a ball portion 27C are connected together.

The fixing pin 27 functions to prevent the peeling of the pad during asubsequent ball bonding, which will be described later.

Referring to FIG. 5F, the secondarily-etched second insulation layer 24Bis recessed by a wet etch process. The wet etch process is performeduntil the disk portion 27A of the fixing pin 27 is exposed. For example,the wet etch process is performed using fluoric acid (HF) or a solutioncontaining fluoric acid (HF). Due to a thirdly-etched second insulationlayer 24C being recessed by the wet etch process, the disk portion 27Aof the fixing pin 27 is exposed.

Referring to FIG. 5G, a third metal layer 28 is formed over thethirdly-etched second insulation layer 24C and is then etched.Accordingly, the bottom surface of the third metal layer 28 is coupledto the fixing pin 27. Meanwhile, during the formation of the third metallayer 28, surface unevenness may occur due to the fixing pin 27, causinga bonding failure. The third metal layer 28 is planarized by a chemicalmechanical polishing (CMP) process or the like. It should be noted thatthe planarization process is carefully performed not to expose the upperportion of the fixing pin 27.

Referring to FIG. 5H, a ball bonding 29 is performed on the third metallayer 28.

Pressure 30 generated by the ball bonding 29 is transferred to thethirdly etched second insulation layer 24C and the slits 23, and arepulsive force 31 is transferred to edges of the third metal layer 28.

Even though the repulsive force 31 is transferred to the edges of thethird metal layer 28, pad peeling is prevented because the edges of thethird metal layer 28 are fixed by the fixing pins 27. That is, when therepulsive force 31 is transferred to the edges of the third metal layer28, the attachment force between the fixing pins 27 and the edges of thethird metal layer 28 is increased because the disk portion 27A of thefixing pin 27 has a shape of a wine glass, thereby preventing the padfrom peeling. Furthermore, since the ball portion 27C of the fixing pin27 has a diameter greater than the size of the gap between the slits 23,the fixing pins 27 are not removed and thus the peeling of the thirdmetal layer 28 is further prevented. Reference numerals 24D and 28Arespectively refer to a recessed second insulation layer and atransformed third metal layer deformed by the pressure generated by theball bonding 29.

FIG. 6A illustrates a plan view of a bonding pad in accordance with asecond embodiment of the present invention. Fixing pins 203 are formedat upper and lower sides of the bonding region 202, as well as at rightand left sides of the bonding region 202.

The bonding pad 200 in accordance with the second embodiment of thepresent invention includes multiple metal layers 201 and insulationlayers (not shown) filled between the multiple layers 201. The fixingpins 203 are coupled between the uppermost metal layer and theunderlying metal layers at an outer area outside of a bonding region202. Although not illustrated, like the first embodiment of the presentinvention, the multiple metal layers include a first metal layer, aplurality of slits formed of a second metal layer, and a third metallayer. The fixing pins 203 are coupled between the third metal layer andthe slits.

FIG. 6B illustrates a perspective view of the fixing pin in accordancewith the second embodiment of the present invention. The fixing pin 203includes a disk portion 203A, a pillar portion 203B, and a ball portion203C.

Like the first embodiment of the present invention, the bonding pad 200in accordance with the second embodiment of the present invention canprevent the pad from peeling. In particular, the second embodiment canfurther increase the peeling prevention effect compared with the firstembodiment because four fixing pins are provided at the outer area ofthe bonding region.

FIG. 6C illustrates a plan view of a bonding pad in accordance with athird embodiment of the present invention. A plurality of fixing pins213 is formed at an outer area of a bonding region 212.

The bonding pad 210 in accordance with the third embodiment of thepresent invention includes multiple metal layers 211 and insulationlayers (not shown) filled between the multiple layers 211. At least fourfixing pins 213 are coupled between the uppermost metal layer and theunderlying metal layers at an outer area outside of a bonding region212. Although not illustrated, like the first embodiment of the presentinvention, the multiple metal layers include a first metal layer, aplurality of slits formed of a second metal layer, and a third metallayer. The fixing pins 213 are coupled between the third metal layer andthe slits.

Like the first embodiment of the present invention, the bonding pad 210in accordance with the third embodiment of the present invention canprevent the pad from peeling. In particular, the third embodiment canfurther increase the peeling prevention effect compared with the firstand second embodiments because the plurality of fixing pins is providedat the outer area of the bonding region 212.

FIG. 7A illustrates a plan view of a bonding pad in accordance with afourth embodiment of the present invention. A fixing pin 303 has acircular ring shape to enclose an outer area of a bonding region 302.

FIG. 7B illustrates a plan view of a bonding pad in accordance with afifth embodiment of the present invention. A fixing pin 403 has apolygonal ring shape to enclose an outer area of a bonding region 402.

FIG. 8A illustrates a plan view of a bonding pad in accordance with asixth embodiment of the present invention. FIG. 8B illustrates aperspective cross-sectional view taken along line A-A′ of FIG. 8A. FIG.8C illustrates a perspective view of a fixing pin in FIG. 8A. FIG. 8Dillustrates a perspective view of a second metal layer in accordancewith the sixth embodiment of the present invention.

Referring to FIG. 8A, a bonding pad 500 includes multiple metal layers501 and insulation layers (not shown) filled between the multiple metallayers 501. A fixing pin 503 is coupled between the uppermost metallayer and the underlying metal layers at an outer area beyond thebonding region 502.

The multiple metal layers 501 include a first metal layer, a secondmetal layer, and a third metal layer.

Referring to FIGS. 8B and 8C, the bonding pad 500 includes the firstmetal layer 501A, the second metal layer 501B, and the third metal layer501C. The first metal layer 501A, the second metal layer 501B, and thethird metal layer 503C are formed in a plate shape. While the secondmetal layer in accordance with the first embodiment of the presentinvention is formed in a slit shape, the second metal layer 501B inaccordance with the sixth embodiment of the present invention is formedin a plate shape. In order to form the fixing pin 503 passing throughthe second metal layer 501B, the second metal layer 501B is patterned toform a hole (H in FIG. 8D) that is large enough to allow the pillarportion of the fixing pin 503 to pass through, and a subsequent processof forming a contact hole is then performed. In another method, thesecond metal layer 501B may be etched during the process of forming thecontact hole. However, such a method may cause the deformation of thecontact hole that has been previously formed during the etching of thesecond metal layer 501B. Therefore, it is preferable that the secondmetal layer 501B is previously patterned to form the hole H.

The fixing pin 503 is coupled between the third metal layer 501C and thesecond metal layer 501B. Specifically, the upper portion of the fixingpin 503 is inserted into and fixed to the lower portion of the thirdmetal layer 501C, and the lower portion of the fixing pin 503 passesthrough the second metal layer 501B and is fixed to the bottom surfaceof the second metal layer 501B.

Referring to FIG. 8C, the fixing pin 503 includes a disk portion 503A, apillar portion 503B, and a ball portion 503C. The disk portion 503A ofthe fixing pin 503 is inserted into and fixed to the lower portion ofthe third metal layer 501C, and the pillar portion 503B of the fixingpin 503 is formed in a cylindrical shape and passes through the secondmetal layer 501B. The ball portion 503C of the fixing pin 503 is coupledto the pillar portion 503B passing through the second metal layer 501B.

Since the disk portion 503A has a rounded lower portion and is coupledto the pillar portion 503B, the fixing pin 503 is formed in a shape of awine glass. The ball portion 503C has a diameter greater than the pillarportion 503B passing through the second metal layer 501B. Accordingly,it is possible to prevent the fixing pin 503 from being removed. It canbe said that the disk portion 503A has a shape of a screw head.

In the bonding pad 500 in accordance with the sixth embodiment of thepresent invention, the fixing pin 503 can prevent the uppermost metallayer, i.e., the third metal layer 501C, from being peeled during thebonding process.

Furthermore, since the disk portion 503A of the fixing pin 503 has therounded lower portion, the attachment force between the fixing pin 503and the third metal layer 501C is further increased. Since the diameterof the ball portion 503C is large enough to prevent the second metallayer 501B from being removed, the third metal layer 501C coupled to thefixing pin 503 is not removed.

In accordance with the above-described embodiments of the presentinvention, the attachment force (that is, a mechanical strength) of thebonding pad is increased due to the fixing pin coupled to the edges ofthe bonding pad where the ball bonding is performed, thereby preventingthe pad from peeling.

Moreover, since the fixing pin has the disk portion and the ballportion, the attachment force between the fixing pin and the bonding padcan be further increased.

As described above, the peeling of the bonding pad can be preventedduring the ball bonding by forming the fixing pin coupled to the edgesof the bonding pad.

Furthermore, since the upper portion of the fixing pin is formed in adisk shape and the ball portion of the fixing pin is fixed by the slits,the peeling of the bonding pad can be further prevented.

Consequently, since the peeling of the bond pad is prevented, the yieldof the package can be improved and the fabrication cost can be reduced.

While the present invention has been described with respect to thespecific embodiments, the above embodiments of the present invention areillustrative and not limitative. It will be apparent to those skilled inthe art that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention as defined in thefollowing claims.

1. A bonding pad, comprising: multiple metal layers; insulation layersdisposed between the multiple metal layers; and a fixing pin coupledbetween an uppermost metal layer and an underlying metal layer of themultiple metal layers, wherein a bonding is performed on the uppermostmetal layer.
 2. The bonding pad of claim 1, wherein the uppermost metallayer comprises a plate-type metal layer, and the underlying metal layercomprises a slit-type metal layer having a plurality of slits formedtherein.
 3. The bonding pad of claim 2, wherein the fixing pin iscoupled between an edge of the plate-type metal layer and an edge of theslit-type metal layer.
 4. The bonding pad of claim 1, wherein theunderlying metal layer comprises a plurality of slits arranged atpredetermined intervals, and the fixing pin comprises a disk portion, apillar portion coupled under the disk portion, and a ball portioncoupled under the pillar portion.
 5. The bonding pad of claim 4, whereinthe disk portion is inserted into and fixed to a lower portion of theuppermost metal layer, the pillar portion passes through a gap formedbetween the slits, and the ball portion is coupled to the pillar portionand formed under the slits.
 6. The bonding pad of claim 5, wherein adiameter of the ball portion is greater than a size of intervals betweenthe slits.
 7. The bonding pad of claim 1, wherein the fixing pin coupledto the uppermost metal layer and the underlying metal layer comprises adisk portion, a pillar portion coupled under the disk portion, and aball portion coupled under the pillar portion.
 8. The bonding pad ofclaim 7, wherein the disk portion is inserted into and fixed to a lowerportion of the uppermost metal layer, the pillar portion passes throughthe underlying metal layer, and the ball portion is coupled to thepillar portion.
 9. The bonding pad of claim 8, wherein a diameter of theball portion is greater than a diameter of the pillar portion.
 10. Thebonding pad of claim 1, wherein the fixing pin comprises a conductivelayer.
 11. The bonding pad of claim 1, wherein the fixing pin comprisesa tungsten layer. 12-18. (canceled)